ON THE HIGH-TEMPERATURE OXIDATION OF POLYCRYSTALLINE AND SINGLE-CRYSTAL NICKEL AFTER ION-IMPLANTATION

The effects of ion implantation on the high temperature oxidation beha viour of Ni have been investigated for a number of species using both polycrystalline and single crystal samples. Kr and Ni have been implan ted to study the physical effects of implantation, while Si and Mg hav e been chosen to study the chemical effects. The ion implantations wer e carried out at 100 keV to a dose of 1x10(17) ions/cm(2) for all the species, and the oxidation experiments were performed at 700 degrees C in oxygen for various times. The oxidation behaviour of polycrystalli ne samples was complicated by the presence of different substrate grai ns and grain boundaries. The oxidation of single crystal samples, on t he other hand, was a less complicated case which allowed a more detail ed study of oxidation mechanisms. In this latter case, results showed that the presence of a high concentration Mg or Si may exhibit reactiv e element effects in blocking the out-diffusion of Ni cations so as to reduce the oxidation rate and promote the formation of a two-tier oxi de structure in which the inner oxide is oriented with the underlying nickel crystal.